A slide rail device for a vehicle disclosed in Patent Literature 1 is equipped with a pair of left and right lower rails which extend in a forward/rearward direction, are fixed to a vehicle interior floor, and include a large number of lock grooves, arranged in the forward/rearward direction; a pair of left and right upper rails which support the seating portion of a seat and are slidably supported by the pair of left and right lower rails; a pair of left and right lock levers which is rotatably supported on the left and right upper rails about an axis that extends in the leftward/rightward direction, which is disengageably-engageable with the lock grooves and, except the front end portions thereof, are each provided in an internal space of the associated upper rail; a biaser provided in the internal space of each upper rail and which rotatably biases the locking lever toward a direction of engagement with the lock grooves; and an operational lever (loop handle), having an approximately U-shape in a plan view, the left and right rear end portions thereof being mounted to the front end portions of the left and right lock levers (the portions that project forwardly from the upper rails).
When an occupant applies no operating force to the operational lever, the sliding of the upper rail relative to the lower rail is restricted since the lock lever is engaged with some of the lock grooves by the biasing force of the biaser. On the other hand, upon an occupant pulling up the operational lever, since each lock lever is released from the engagement with the lock grooves against the biasing force of the biaser, the upper rails can slide relative to the lower rails.